Accurate Titanium Parts Make: What It Takes on the Shop Floor

Titanium has a low thermal conductivity, around 7 W/m·K for Ti-6Al-4V. Heat does not leave the cut zone quickly. It builds at the edge, softens the tool, and pushes the workpiece as the part grows. A roughing pass that works in 6061 will burn a carbide insert in Ti-6Al-4V within minutes.

The alloy also has a low elastic modulus, roughly 110 GPa. Thin walls and long slender features deflect under cutting force and spring back after the tool passes. A 1.5 mm wall on a titanium housing may measure correctly on the machine and move 0.03 mm after unclamping.

Most titanium parts that miss tolerance do not miss it because the machine was inaccurate. They miss it because the process plan ignored heat, clamping and tool wear. Fix those three and the same machine will hold ±0.005 mm all day.

Setup count is the largest single error source on titanium. Every reclamp introduces a new datum, and titanium's springback makes each datum slightly different. A part that needs six setups on three-axis machines accumulates error at every step.

Simultaneous five-axis machining cuts that down. On a trunnion machine with a Ø400 mm rotary table, we can reach five faces in one setup. Datum shift drops to near zero, and the bores that must align stay aligned because they were cut without the part ever leaving the fixture.

Five-axis also helps with tool access. Titanium parts often have deep pockets and contoured ribs that a three-axis spindle cannot reach without long, flexible tooling. Short, rigid tools with a tilted approach cut cooler and leave a better floor finish. That is where accurate titanium parts make their tolerance budget last.

• 1
  One setup, five facesRemoves datum shift between operations on complex housings and brackets.
• 2
  Short tool overhangTilted approach lets us use stubby end mills instead of long reach tools.
• 3
  Better chip evacuationGravity-assisted chip flow in deep pockets reduces recutting and heat.
• 4
  Consistent floor finishContinuous contact on contoured surfaces avoids witness marks and steps.

Carbide grade matters more on titanium than on aluminum. We run uncoated micro-grain carbide for finishing because coatings can flake at the edge temperatures titanium produces. For roughing, an AlTiN coating works when the pressure is high enough to keep the edge cool.

Tool geometry is the next lever. A positive rake angle with a sharp edge cuts titanium instead of pushing it. That reduces the work-hardened layer that forms when a dull tool rubs the surface. Once that layer forms, the next pass cuts through hardened material and the tool wears twice as fast.

For finishing passes, we leave 0.15–0.25 mm of stock and take it in one continuous pass. Stopping mid-surface on titanium leaves a mark that shows through anodizing. The floor and walls need to be cut without hesitation to hit Ra 0.8–1.6 μm as machined, or Ra 0.2–0.8 μm after polishing.

Titanium moves after machining. A part that measures on the machine may relax overnight. We let critical parts stabilize at room temperature before final inspection, especially thin-wall geometries and parts with large removed volumes.

Inspection runs on a CMM with temperature compensation, and we check the features that carry function first: bore diameters, flatness on sealing faces, position of mounting holes. A report can be issued on request, with the datum scheme stated so the customer's incoming inspection matches ours.

Every part is inspected before shipment, not sampled. Raw material certificates are checked at receiving, in-process checks catch drift during long runs, and final inspection signs off the geometry. The qualification rate across titanium production is 99.99%.

Titanium earns its cost when the part needs high strength at low weight and will see corrosive service. Aerospace brackets, medical implants, and motorsport suspension components are typical. Ti-6Al-4V gives roughly the strength of 4140 steel at 57% of the density.

It is the wrong choice when the part is mostly cosmetic, when the geometry is a simple prismatic block, or when the budget is tight and aluminum would pass the load case. Titanium stock costs 5–10× more than 6061, and machining time runs 3–5× longer. A part that does not need the corrosion resistance or the strength-to-weight ratio will not justify that.

For parts that sit between aluminum and titanium on the requirement list, 17-4PH stainless or 7075 aluminum often close the gap. We will say so during DFM review rather than quote a titanium part that should have been aluminum.